To make a full backup you can use exp sys/pwd@base full=y.
You can also do a cold backup :
Stop the database
save redolog file, datafile, controlfile, ini.ora
restart the database.
If your db crash, you can recreate one db (with dbca) and reimport file, or use cold backup + archive.
See : http://asktom.oracle.com/pls/ask/f?p...:3151992035532